You have not actually proven it is an Rinnegan technique but simply made a deduction based on the word "Heavenly", it is an erroneous deduction as not only have you disregarded the Handseals made by susano'o [
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Tatsu, the Dragon seal and
Tairitsu no In which represents half of a seal that can be used
to activate a ninjutsu. The technique itself cannot be used outside of susano'o as not only was Nagato a rinnegan user unable to perform the technique but Madara had to activate His susano'o and cast these seals for the Meteorites to actually appear. There is also other canonical evidence pointing towards it being a technique Madara wielded prior to activating the rinnegan being:
-> Shikaku having no knowledge that madara possessed the rinnegan immediately and without second thought, attributed the "Doton like" technique as Madara's jutsu only implying that He has conducted research/come across such a jutsu that may have been used in the past by madara. His credibility is one of the best in the series [
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> Madara's recollection that the sight of his two meteors as "A view he hasn't enjoyed in a long time" implying that he has used the jutsu prior to Awakening the Rinengan as we have been told exactly what events occurred after the doujutsu's birth in his old age [
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A Similar misconception was made when majority held the belief that Perfect Susano'o was a Rinnegan based technique due to it being prominent at the point of activation. The evidence is clearly against your theory. Following up on events when Madara used the jutsu:
-> He activated the Rinnegan to absorb naruto Rasen-Shuriken
-> He activated Susano'o
-> Weaved handseals along with Susano'o
Then the appearance of the two meteorites occurred.